Network namespaces and scripts seem to break $PATH [duplicate]

Question

Assume the following script:

$ cat test.sh
#!/bin/bash
echo $PATH

This happens:

$ echo $PATH
/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/<user>/.local/bin:/home/<user>/bin
$ sudo ip netns exec blue echo $PATH
/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/<user>/.local/bin:/home/<user>/bin
$ ./test.sh
/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/<user>/.local/bin:/home/<user>/bin
$ sudo ip netns exec blue ./test.sh
/sbin:/bin:/usr/sbin:/usr/bin

Why. It's breaking my scripts ecosystem because it means they cannot see many of my binaries.

Out of the two distributions I've tested this in, Fedora 24 is the only one that does it. Ubuntu 14.04 echoes all $PATHs the same as I expect.

I tried adding to the script

$ sudo ip netns exec blue PATH=$PATH

But it errors out, presumably because PATH=etcetc is not really a command.

What is the correct way to do it?

Answer 1

You can always do two things: Use the fully qualified name of the command, thus there is no doubt. In any of my scripting, I specifically set the PATH variable inside the script to avoid problems with external modifications to the environment (i.e. be independent of the environment). This seems to be a good general practice anyway.